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Hydrogen

Short Answer Type

151.

Complete the following chemical reactions.
PbS + H₂O₂ (aq) $rightwards arrow$

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152.

Complete the following chemical reactions.
$MnO subscript 4 superscript minus left parenthesis aq right parenthesis space plus space straight H subscript 2 straight O subscript 2 left parenthesis aq right parenthesis space rightwards arrow$

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153.

How does hydrogen peroxide act as bleaching agent?

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154.

Give two chemical reactions which show the acidic character of hydrogen peroxide.

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155. Hydrogen peroxide is used to restore the colour of old oil paintings containing lead oxide. Write a balanced equation for the reaction that takes place in this process.

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Long Answer Type

156. What is the structure of hydrogen peroxide? Draw a schematic diagram indicating the shape of the molecule clearly.

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157.
Compare the structure of H₂O and H₂O₂

(i) In H₂O molecule, the central oxygen atom is sp² hybridised and it is surrounded by two bond pairs and two lone pairs. The presence of two lone pairs brings distortion in the geometry of the molecule. Since the lone pairs repel the bond pairs more effectively resulting in the decrease of H – O - H bond angle from 109.5° to 104.5°, thus water is a bent molecule.

(ii) The structure of H₂O₂ is like that of an open book. The O – O part of the molecule can be thought of as lying on the spine of a book open at an angle of 90°. The hydrogen atoms are placed one on each cover. The H – O bonds make an angle of about 101.5° with the O – O bond as shown. The O – O linkage present between two oxygen atoms is called peroxide linkage. The structure of hydrogen peroxide in the gas phase and the crystalline state are as shown below.